Electric discharge device for the amplification of short waves



1950 K. s. KNOL ET AL ELECTRIC DISCHARGE DEVICE FOR THE AMPLIFICATION OFSHORT WAVES Filed March s, 1948 OUTPUT C/RCU/T INPUT CIRCUIT INVEN TORJ KORNELI-S swam KNQL 5v ALBERT VAN DER Z/EL A TTORNEY.

Patented Nov. 21, 1950 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE DEVICE FOR THE AMPLIFICATION OF SHORT WAVES Kornelis Swier Knol and Aldert van der Ziel, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford,

Conn., as trustee Application March 3, 1948, Serial No. 12,774 In the Netherlands March 7, 1947 3 Claims. 1

This invention relates to amplifying circuits for ultrashort waves, in which use is made of a, tube comprising a cathode, an anode, and at least one grid arranged between the control grid and the anode and having a positive potential with respect to the cathode. In order to avoid harmful reaction of the anode upon the input circuit of the tube, it is known to earth the said grid of positive potential (the screen grid) for the highfrequency oscillations to be amplified through a capacity provided in the tube. In tubes with so-called cathode-basis connection, in which the cathode is earthed, this is effected by connecting the said capacity between the screen-grid and the cathode. In tubes with so-called gridbasis connection, in which the control grid is earthed as far as high-frequency currents are concerned, the said capacity is provided between the screen grid and the control grid.

In the case of amplifiers for use on ultrashort waves it is common practice to form the lead-in conductors for the electrodes in the shape of rings, discs, cylinders or a plurality of parallel pins in order to minimise the inductance and the resistance. As a matter of course, in such constructions a large number of lead-in conductors involves disadvantages.

The invention is based on recognition of the fact that in amplifiers comprising tubes of this kind it is possible to reduce the number of connection contacts of the tube by one by connecting the screen grid to the anode through an inductance provided in the tube, if only care is taken to ensure that the impedance of the inductance for the frequency to be amplified has a high value with respect to the natural capacity between the anode and the screen grid. In this case the direct-voltage supply of the screen grid is effected via the anode.

In order that the invention may be clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing in which:

Fig. 1 shows an amplifier circuit arrangement according to the invention and having a grounded cathode,

Fig. 2 shows another amplifier circuit according to the invention and having a grounded control grid, and

Fig. 3 shows a cross sectional view of a tube according to the invention.

Fig. 1 shows an amplifying circuit having an amplifying tube l which comprises a cathode 2, a control-grid 3, a screen-grid 4 and an anode 5. The control-grid 3 and the earthed cathode are separated by the input circuit 6, in which the oscillations to be amplified occur, whilst the anode 5 and the cathode 2 are separated by the output circuit 1, from which the amplified oscillations are obtained. The screen-grid 4 is not connected directly to a supply conductor led through the envelope of the tube, but it is connected through an inductance 9 provided in the tube between the screen-grid and the anode 5, to the positive terminal of the source of supply, the screen-grid being also connected through a capacity 8 to the cathode. By a suitable choice of the inductance 9 and of the capacity 8 with respect to the natural capacity between the screen-grid 4 and the anode 5 it may be ensured that the screengrid 4 substantially exhibits earth potential with respect to the oscillations to be amplified.

Fig. 2 shows a circuit which is distinguished from that of Fig. 1 in that the control-grid 3 is earthed. The input impedance 6 is here connected between the control-grid and the cathode and the output impedance 1 between the grid and the anode. In this case the additional capacity 8 provided in the tube is to be included between the screen-grid 4 and the control-grid 3.

In the case of an amplifier for waves of the order of magnitude of cms. the inductance 9 may consist of a wire of 25 cms. length wound in the form of a thin coil. The length of this wire is, for example, of the order of magnitude of a quarter of a wavelength.

Fig. 3 shows a cross-sectional View of a tube constructed according to the invention and adapted for use in a grounded-grid circuit as shown in Fig. 2. In Fig. 3 the inductance 9 is connected between the anode 5 and the screen grid 4. The capacity 8 of Fig. 2 is primarily constituted by portion IE! of screen grid 4 which serves as one pl a r of dielectric material H, and control grid 3 which serves as the other plate.

The invention is applicable not only to tetrodes but also to pentodes, hexodes, and so forth.

What we claim is:

1. An electric discharge tube adapted for use in short wave amplifier circuits of the type having an output circuit connected to the anode, and an input circuit connected between two other electrodes; the combination comprising: a sealed envelope; cathode and control grid electrodes one of which is grounded, an anode and at least one screen grid all mounted within said envelope; lead in conductors for said cathode, control grid and anode; an inductance within said envelope connected between said anode and said screen grid;

- a. capacitor within said envelope connected between said screen grid and said grounded electrode, whereby said screen grid exhibits substantially ground potential with respect to the short wave signal being amplified.

2. An electric discharge tube 'dfiifiedi bii claim 1 which the capacitor is connected between the screen grid electrode and the cathode electrode.

3. An electric discharge tube-as. .defined--,,by claim 1 in which the capacitor isf-cofxnected be-l tween the screen grid electrode and the control grid electrode. H V

h s SW EE: SN ALDERT m bin? ZIEL:

4 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number v Name .Date

1,528,735 McCullough M237 3, 1925 2,294,328 Aldous Aug. 25, 1942 2,434,792 Dolberg Jan. 20, 1948 :10 2,455,218 a Briggs Nov. 20, 1948 

